1. Statement of the Technical Field
The present invention relates to a content transformation engine and more particularly to a caching technique utilized in conjunction with a content transformation engine.
2. Description of the Related Art
The growth of the public network such as the Internet has driven corresponding, but exponentially increasing, growth in the generation and distribution of content across the public network. Initially, content had been formatted in one of a handful of content formats and distributed accordingly. Still, with the advent of the World Wide Web and the Web browser, a movement emerged in which content distributed over the Internet could be uniformly formatted using markup tags as in the hypertext markup language (HTML). Nevertheless, as it became apparent that the substance of content ought to remain separate from the formatting and presentation elements of the content, new formatting technologies evolved. Thus, the idea of transforming content from one format to another followed.
In the field of global data communications, the sharing of content can be achieved by expressing that data using the extensible markup language (XML). Once expressed in XML, content can be sampled by multiple interested parties before ultimately becoming consumed. For example, XML content generated by a third-tier server can be sampled by a transcoding publisher acting as a reverse proxy. In consequence, the XML formatted content can be transformed using extensible stylesheet (XSL) technologies into a renderable XML-based grammar such as XHTML or WAP/WML. This renderable XML ultimately can be consumed by a client browser or a pervasive device.
XSL has emerged as a popular and effective model for transforming an XML document into one of another XML document, or a rendered markup language form of the document, for instance WML, VoxML, HTML, etc. Unfortunately, XSL, too, is not without its inherent deficiencies. One significant disadvantage associated with XSL can include the substantial overhead incurred during the transformation of an XML document using XSL. In particular, this overhead can result from the interpretation of scripting as a primary model of operation for XSL technologies. Also, document object model (DOM) traversal and template matching operations within an XSL stylesheet can further complicate matters.
The degree of overhead incurred during an XSL transformation can be measured as a factor of the length of the XML data, the complexity of the transformation rules specified in a XSL stylesheet, and the availability of all constituent entities of the XML document and XSL stylesheet. Notably, network latencies can form a prominent portion of the complexity computation when considering the retrieval of content across a network required during the transformation process. While caching technologies have proven effective in combating network latencies in the distribution of content on the Internet, in the case of XML data, it is during the transformation that overhead can be experienced more so than during the distribution of the content.